JPS6237617B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, phenol is converted into an olefin having 3 to 4 carbon atoms in the liquid phase in two reaction zones connected in front and back to form an alkyl compound at high temperature in the presence of a strongly acidic ion exchange resin as a catalyst. The present invention relates to a method for producing p-alkylphenols by It is known to alkylate phenols in the presence of acids or Lewis acids such as sulfuric acid or boron trifluoride. The use of such catalysts requires, for example, corrosion-resistant equipment and, moreover, the resulting products are not obtained in the required purity and do not have the desired color quality. Therefore, recently, H-type strongly acidic ion exchange resins, especially sulfonated ion exchange resins, such as sulfonated ion exchange resins based on phenol-formaldehyde resins or polystyrene resins, have recently been used for alkylation. . High space-time yields are indeed obtained, but the local overheating of the pronounced exothermic reaction cannot be reliably excluded.
This results in contaminated - especially discolored - alkyl-phenols which are unsuitable for later use. Furthermore, the ion exchange resin is damaged. In the process of DE 1443346 (=Australian Patent No. 259106), the reaction mixture consisting of olefin, phenol and the alkyl-phenol formed is recycled to the reactor through a heat exchanger and Local overheating is avoided by only partially alkylating and then drawing off amounts of olefins and phenols corresponding to the new inflow and reacting further in a second stage. A disadvantage of this process is that it is expensive due to the circulation of the reaction components and the heat load which can lead to decomposition or discoloration of the target product. Furthermore, only low space-time yields can be obtained using this method. According to US Pat. No. 3,257,467, phenols are alkylated with olefins in a single reaction step in an adiabatic reactor in the presence of a strongly acidic ion exchange resin. Catalysts are susceptible to early damage due to localized overheating. Furthermore, in this process only unsatisfactory space-time yields can be obtained. In the case of the method of DE 25 26 644, suspended in a liquid reaction mixture
This is carried out using a cation exchanger with a particle size of 100 to 200 μm. Even if this method achieves good removal of the reaction heat as expected, the yield of the p-alkylated compound is not satisfactory. All these processes have the common drawback that the resulting alkyl-phenols decompose into the starting compounds, possibly due to impurities generated from the catalyst during the subsequent distillation of the reaction products. Not only does this reduce the yield, but also, especially when volatile olefins are produced, it can cause vacuum disturbances in the distillation stage to the extent that work-up is extremely difficult. It was therefore an object of the present invention to prepare p-alkyl phenols having 3 to 4 carbon atoms, which allow the production of qualitatively high-value p-alkylphenols that can be worked up satisfactorily with high selectivity and high space-time yields. The object of the present invention is to find a method for producing p-alkylphenols from olefins and phenols. This problem is solved by the method according to claim 1. In the first reaction stage, the olefin is introduced in gaseous form into the reaction mixture through frits, sieve plates and other suitable distribution devices. This achieves intensive mixing of the reactor contents and keeps the catalyst suspended. The olefin-
The gas has a molecular volume of 25/mol (olefin) of 3 to 20 olefins per free cross-sectional area of the empty reactor.
The olefin should be introduced from below into the reaction mixture at a gas velocity of cm/sec. Below 3 cm/s, the proportion of m-alkylphenol increases significantly, and above 20 cm/s one must be prepared for the formation of disturbing dish-shaped bubbles in the reaction mixture. However, it is advantageous to work at gas velocities as high as possible. The first stage reaction is carried out at a temperature of 80 DEG to 140 DEG C., although a temperature range of 100 DEG to 120 DEG C. is advantageous. This is because the above range is particularly advantageous for the reaction rate and the generation of by-products. Below 80°C, significant by-products are generated, and above 140°C, the possibility of thermal damage to the catalyst increases. As a catalyst, a known organic sulfonic acid-based catalyst can be used.
Cation exchangers, such as sulfonic acid-phenolformaldehyde or benzene-formaldehyde resins, crosslinked sulfonated styrene polymers and particularly preferably sulfonated polystyrene
Divinyl-benzene resin is used. These resins may have a gel-like structure, but resins with a macroreticular (macroporous) structure are advantageous.
The particle size of the catalyst does not affect the reaction. This, of course, assumes that the catalyst is in suspension at the gas velocities mentioned above. This is 0.3~
This applies to readily available commercial catalysts with a typical particle size of 1 mm. If catalysts with larger particle sizes are to be used, simple preliminary experiments can demonstrate whether a floating state of the catalyst is achieved. Ion exchange resins are used dry in acid form. When using commercially available acidic ion exchange resins with an exchange capacity of 130-180 mVal/100 cm ³ , a tendency to decompose into starting products during distillation of the reaction products has been observed. 70～120mVal/
It was surprising to find that such decomposition virtually disappeared when using a reduced ion exchanger having a capacity of only 100 cm ³ and especially 110 mVal/100 cm ³ . Below 70 mVal/100 cm ³ the economics of the process decreases significantly and by-products are formed significantly. Such reduced strength catalysts are obtained when fresh water-moist ion exchange resins are treated with appropriate amounts of salts such as aluminum sulfate, zinc sulfate, tin sulfate, etc., washed, neutralized and dried. Drying is advantageously carried out by removing water by azeotroping with an entrainer such as benzene, cyclohexene, toluene and the like. As it is well known that the water content in the catalyst reduces the catalytic activity, efforts are made to keep the residual water content in the catalyst at 0.5% or less. It is expedient to carry out the reaction with an excess of phenol. Stoichiometric amounts can also be used, but undesirably large amounts of dialkylphenols are then formed. The molar ratio used in phenol:olefin practice is approximately 1.3:1 to 3:1.
Above a molar ratio of 3:1, no additional effect occurs and the phenol is very expensive to distill. A particularly advantageous molar ratio is approximately 2:1. This method can be practiced under any pressure as long as the olefin remains in a gaseous state.
However, normal pressure or a slight excess pressure sufficient to overcome the flow resistance is advantageous. The product from the first process step enters the second process step after separation of the catalyst. Separation of the catalyst can be carried out in the first process step by means of candlestick filters, filter plates and the like, while the reactor can withdraw the catalyst-free product above the catalyst zone. It is also possible to design it so high that a quiet catalyst-free liquid zone occurs. 80～
In the second reaction zone, which is operated at a temperature of 140 DEG C., in particular 120 DEG C., the product from the first process step is treated with a very small proportion of 0-alkyl- and 2,4-dialkyls. To convert the phenol to the desired P-alkylphenol,
It is subjected to an after-reaction with a fixed catalyst of the same exchange capacity as the first process step. The residence time in the second reaction zone should preferably be about 0.5 to 2 hours, while in the first reaction zone residence times of 1 to 3 hours are preferred. However, even longer reaction times have no negative effect on the product. P-alkylphenols produced according to the method of the present invention are important raw materials for producing stabilizers, anti-aging agents, drugs, etc. For example, Kirk Othmer's “Encykulopedia of Chemical Technology” 2nd edition, Volume 1, pp. 901-916 or “Ullmann's Encyclopedia of Chemical Technology”. Der Technicie
Ullmanns Encyclopaedie der
Technischen Che-mie)”, Volume 13, Nos. 440-447
(1962). Example 1 This example demonstrates the effect of gas velocity in the initial reaction zone. A reactor with an internal diameter of 3 cm and a height of 100 cm is filled with a dry macroporous ion exchange resin with a capacity of 110 mVal/100 cm ³ . The catalyst has a particle size of 0.3 to 1 mm. The reactor is charged with phenol and then various amounts of phenol and isobutylene are added through a glass fritter at the bottom of the reactor at a reaction temperature of 115°C. After achieving quiescent conditions, the product withdrawn from the top of the reactor (experiments a to c) has the composition (calculated on the basis of phenol-free content) as can be seen from Table 1. Another experiment d with even faster reaction rates was carried out using the same catalyst at the same reaction temperature in a reactor with an internal diameter of 70 cm and a height of 450 cm and containing 200 Kg of ion exchange resin. do. This result can also be known from Table 1.

【table】

[Table] Examples 2 to 7 Inner diameter 3 filled with 92 g of macroporous cation exchanger having the exchange capacity as shown in Table 2
cm, 450 g of phenol per hour in a 100 cm high glass reactor (first reaction stage)
75 g of isobutylene is introduced through a frit at the bottom of the reactor. The gas velocity of isobutylene is
80-130°C and the molar ratio of phenol:isobutylene is 1.9:1. Products arising from the glass reactor (unreacted phenol, o-tertiary, m-tertiary and p-tertiary)
-butylphenol and 2,4-di-tert-butylphenol) with an inner diameter of 5 cm,
A further reactor (second reaction stage) with a height of 50 cm and in which 350 g of macroporous catalyst is placed in a fixed manner is introduced. The product resulting from this reactor can be subjected to distillation without further treatment. The results are shown in Table 2.

Table of Contents Examples 8 and 9 These examples demonstrate the improvements according to the invention that are observed during distillation processing of products made according to the invention. Similar to Examples 2 to 7, the alkylation is carried out in the first stage at a temperature of 115°C and in the second stage at a temperature of 120°C. In Example 8, a catalyst with an exchange capacity of 110 mVal/100 cm ³ was used according to the present invention, and in Example 9, according to the prior art, a catalyst with an exchange capacity of 140 mVal/100 cm 3 was used.
A catalyst with an exchange capacity of 100 cm ³ is used. The products obtained in each case are treated by distillation. A packed column with an inner diameter of 60 cm and a height of 1 m is used as the distillation column. This distillation is carried out under a pressure of 33 mbar. The separated isobutylene is condensed in a receiver cooled to -78°C and then weighed. The results are shown in Table 3.

【table】

Claims (1)

[Scope of Claims] 1. Phenol is reacted with an olefin having 3 to 4 carbon atoms at high temperature in the liquid phase in two reaction zones connected in front and behind in the presence of a strongly acidic ion exchange resin as a catalyst. In the preparation of p-alkylphenols by alkylation with at gas velocity
80-140 while introducing the olefin with a molecular volume of 25/mol (olefin) into the reaction mixture from below.
in contact with a catalyst present in suspension at a temperature of 80°C to 140°C, and the liquid reaction product obtained is transferred in a second reaction stage onto a fixedly placed catalyst at a temperature of 80 to 140°C. The process for producing p-alkylphenols as described above, characterized in that a catalyst with an exchange capacity of 70 to 120 mVal/100 cm ³ is used in both the reaction steps. 2. A process according to claim 1, wherein the temperature of the first reaction zone is 100-120C and the temperature of the second reaction zone is 120C. 3. The method according to claim 1 or 2, wherein the catalyst has an exchange capacity of 110 mVal/100 cm ³ .